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U.S. Army Research, Development and Engineering Command Dr. Eric Kathe, US Army RDECOM-ARDEC’s Benet Labs NDIA, April 2015 Cutting Down the Kick: Understanding and Managing Large Caliber Recoil
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Page 1: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

U.S. Army Research, Development and Engineering Command

Dr. Eric Kathe, US Army RDECOM-ARDEC’s Benet Labs

NDIA, April 2015

Cutting Down the Kick:

Understanding and Managing Large Caliber Recoil

Page 2: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German
Page 3: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Some Examples of Light Vehicles

General Dynamics

Stryker

Light Armored Vehicle with 105mm

M68 gun

United Defense

M8 Armored Gun System

Light Tank

with 105mm M35 gun

German Wiesel

Airportable Armored Vehicle

with 7 TOW ATGM Missiles

Page 4: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Why?

• Gun Weight • Recoil Force • Vehicle Stability • Thermal Management

• Gun Weight • Recoil Force • Vehicle Stability • Thermal Management

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Catch 22

• Airborne Rule:

– Must fit on C130

• Weight limited to < 20ton

• Design of Fighting Vehicle Rule:

– Recoil Should Not Exceed 900 Ns/Metric Ton

• The impulse of a current 120mm tank cannon requires about 32 tons.

• New suspension/ergonomic technology is enabling modest increases in impulse to weight rules of thumb.

Page 6: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Projectile

Charge Gases Recoiling Parts

External

Force Applied

to Gun Conservation of Momentum

Momentum Imparted to Projectile and

Propellant Gases must be Equal and Opposite to

That Imparted to a Freely Recoiling Cannon.

mgun vgun + mcharge vcharge + mprojo vprojo = 0

Basics of Recoil Momentum

Depiction of gun recoil [4].

therefore… vgun = (S Launch Momentum)/ mgun

Page 7: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Recoil Momentum and Energy

• Momentum imparted to the cannon during firing is manifest as kinetic

energy.

KE = 1/2 mgun v2

gun

OBSERVATION: For a given momentum, the kinetic energy of a

recoiling gun is inversely proportional to its mass.

Page 8: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

0 500 1000 1500 2000 2500

Recoiling Cannon Mass [Kg]

0

50

100

150

200

250

300

350

400

500

Kin

etic E

ne

rgy o

f R

eco

il [K

J]

Conventional Gun Steel

Carbon Fiber Composite

Potential Weight Reduction with Composites

Composite RAVEN

120mm

120mm With

Brake

Current

120mm

1

2

3

4

5

6

Ge

e L

oa

din

g o

n 1

7to

n V

eh

icle

A

ssu

min

g ½

m (

20

”) R

eco

il S

troke

Composite

120mm With

Brake

450

Page 9: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

The Role of a Recoil System

• Recoil systems extract the kinetic energy over the available recoil stroke.

KE = fFrecoil dx Stroke

Flat recoil force profiles result in the lowest maximum

load for a given recoil stroke.

Fo

rce

Recoil Force Versus Stroke

KE y FrecoilGXstroke

Stroke

Page 10: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Methods of Recoil Mitigation

Two Paths:

• Recoil Reduction: Reduce the launch momentum.

– muzzle brakes.

– RArefaction waVE GuN (RAVEN).

• Recoil Management: Deal with recoil more effectively.

– Increase recoil stroke.

– Increase recoil mass.

– Improve vehicle/ground interface.

– Improve man-machine interface.

Page 11: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Momentum Reduction Methods

MMMUUUZZZZZZLLLEEE

BBBRRRAAAKKKEEESSS

Reduced or Reversed Forward Momentum of Charge Gas at/near end of Ballistic Cycle

RRREEECCCOOOIIILLLLLLEEESSSSSS

GGGUUUNNNSSS

Rearward Momentum of Charge Gas or Dummy Projectile During Ballistic Cycle

LLLIIIGGGHHHTTT WWWEEEIIIGGGHHHTTT

PPPRRROOOJJJEEECCCTTTIIILLLEEESSS

Reduced Forward Momentum of Ordnance Projectile &/or Ancillary Structure (e.g. sabots)

Page 12: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Muzzle Brakes

• Typical muzzle brake reduces launch momentum

by 20%

• Blast overpressure and obscuration principle

disadvantages.

Projectile

Charge Gases

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Recoilless Guns

• Inefficient ballistics results in

charge masses four times

closed breech gun

requirements.

• High signature and dangerous

back blast.

Projectile

Some of the Charge

Gases Most of the Charge

Gases

Page 14: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

RArefaction waVE guN

RAVEN is a hybrid propulsion that achieves: – The thermodynamic efficiency of orthodox guns.

– The recoil advantage of prior recoilless rifles.

– Unprecedented reductions in barrel heating.

– Blast reduction.

“Rarefaction Wave Gun Propulsion,” Kathe, Dillon, Sopok, Witherell, and Dunn,.

http://handle.dtic.mil/100.2/ADA389156

“Sonic Rarefaction Wave Low Recoil Gun,” Kathe and Dillon,

http://handle.dtic.mil/100.2/ADA398942

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Late Venting Doesn’t Slow the

Bullet

If the breech of the chamber of a gun is suddenly opened while the projectile is being propelled down the bore, a delay time will occur before the pressure loss at the chamber can be communicated forward to the base of the projectile.

-2 0 2 4 6 8 10

0

50

100

150

200

250

300

350

400

Pre

ssure

[M

Pa

]

Time [ms]

Shot Exit

Venting

Actual Chamber Pressure Data Vented and Non-vented Rounds With Same Muzzle Velocity

58 ksi peak Wave Front

Projo.

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Experimental Results

Ejection of

Cartridge Case Head.

Ejection

of Cartridge Case Body,

Bolt Returning to Battery.

Firing

and Venting.

Fir

ing

Vid

eo

Se

qu

en

ce

Fra

me

: 1

9

Fra

me

: 9

Fra

me

: 0

Fra

me

:-

1

630

ms

300

ms

0m

s

-33m

s

Before

Firing.

Ejection

of Cartridge Case Body,

Bolt Returning to Battery.

Bolt-Action Blow-Back Bolt for Proof of Principle

Ph.D.

Rensselaer 2002

NATO Standard 35mm Training Round

Muzzle Velocity

Vented 1,131 m/s

Non-Vented 1,135 m/s

Barrel Heating (ΔT)

Vented 2.13K Non-Vented 3.61K

Measured Momentum

Vented 402 Ns

Non-Vented 1,031 Ns

“Experimental Validation Of Raven Using Standard 35mm Nato TP Ammunition,” Kathe, Glennon, Tortorici, Kertis, and Stamm, JANNAF 38

th Combustion Meeting, Destin, FL, 08 April 2002.

Page 17: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Recoil Management Methods

INCREASED

RECOIL MASS

Recoil energy inversely proportional to recoiling mass

INCREASED

STROKE

Recoil loads inversely proportional to recoil stroke.

FIRE OUT OF

BATTERY

Pre-acceleration of recoiling mass may reduce recoil velocity by as much as 50% with 75% reduction in kinetic energy

ACTIVE

SUSPENSION

Active recoil mitigation suspension may enable vehicle to tolerate greater recoil momentum

Page 18: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Increased Recoil Mass

• Increased recoiling mass is counter productive for

lightweight weapon platforms.

• The potential to leverage “some other” inertia

(such as armor) using a double recoil is intriguing,

yet challenging to implement.

A Double Recoil

Leverages a Second

Sprung Mass.

Page 19: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Increased Stroke

• Increased recoil stroke increases under armor

volume, but is viable for external guns and special

applications.

Page 20: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Turret Integration

• A gun must fit within a turret such that room exists behind the gun sufficient:

– To prevent impact at max recoil extent at all elevations.

– To enable munitions to be loaded.

Page 21: Cutting Down the Kick - ... · PDF fileCutting Down the Kick: ... Light Armored Vehicle with 105mm M68 gun United Defense M8 Armored Gun System Light Tank with 105mm M35 gun German

Fire out of Battery M35

The M35 105mm Tank Gun

A novel recoil method was applied where the cannon was pre-accelerated forward prior to firing. Upon firing, the forward motion of the cannon was reversed, sending it back to a catch latch. This approach may theoretically reduce recoil by a factor of four. By splitting the momentum in half, the max recoil velocity is cut by two, and the kinetic energy is cut by four. Practical consideration reduce performance to a factor of two. Over a 40% reduction was achieved in test.

WEIGHT: …………………..~ 2920 LBS

BARREL LENGTH…………220.5”

RECOIL LENGTH: …………22”

OPERATING PRESSURE: …~90 KSI

“A Fire Out-of-Battery Tank Gun: Theory and Simulation,” Kathe, and Gast,

http://handle.dtic.mil/100.2/ADA402105

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Questions

• Thank you for the opportunity to present a tutorial on recoil today.

• Questions are welcome.


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